Influence of human menopausal gonadotropin on the recruitment of human ovarian follicles

Human menopausal gonadotropin (hMG) was administered once (225 IU) to 16 women during different phases of the menstrual cycle: either late-luteal, early-follicular, midfollicular, or late-follicular phases before surgical ovarian resection or ablation. The mitotic index (MI) of follicular granulosa cells and the proportion of recruitable healthy follicles were analyzed 4 to 5 days after hMG injection, the findings being compared with those in unstimulated ovaries from 22 normally cycling patients. The percentages of healthy recruitable follicles greater than or equal to 2 mm in diameter was not altered by hMG as compared with controls. The granulosa cell MI was highly stimulated by hMG when administered in late-luteal or early-follicular phases; however, no granulosa cell MI stimulation was noted when hMG was administered in the midfollicular or late-follicular phases. The progressive abolition of the ability of hMG to stimulate follicular growth as ovulation approaches supports the existence of an inhibitory activity (possibly ovarian) designed to suppress the selection and the maturation of the less developed antral follicles from the midfollicular phase of the spontaneous human menstrual cycle.